The extracellular space (apoplast) in plants is a key battleground during microbial infections. To avoid recognition, the bacterial model phytopathogen Pseudomonas syringae pv. tomato DC3000 produces ...

Agroinfiltration of Nicotiana benthamiana is routinely used for transient gene expression in plant sciences and molecular pharming. Here, we depleted transcripts of 21 different immunity-related genes through virus-induced gene silencing (VIGS) to identify genes that hamper transient expression in juvenile plants. These experiments uncovered that silencing of ethylene insensitive-2 (EIN2), receptor-like kinase CERK1, transcription factor regulator nonexpressor of pathogenesis-related genes 1 (NPR1) and isochorismate synthase (ICS), increases transient GFP expression by 2-, 4-, 4- and 11-fold, respectively. Accordingly, the npr1a/npr1b double mutant of N. benthamiana does indeed facilitate increased protein accumulation when transiently expressed. These results indicate that glycan perception through CERK1, and ET and SA signaling pathways via EIN2 and NPR1/ICS, respectively, contribute to suppressed transient gene expression in frequently used juvenile N. benthamiana plants. ### Competing Interest Statement The authors have declared no competing interest.

Plants recognize bacteria by perceiving a 22-residue epitope in flagellin. Plant-secreted SBT5.2 subtilases are found to inactivate this epitope, leading to elicitor removal and reducing costly immuni...